My astronomy teacher said that without plate techtonics, complex life on a planet can't last very long to the best understanding of astrobiologists..

She said that since the surface isn't being subducted and replenished, all the carbon from the atmosphere will end up getting pumped out of the atmosphere into the crust and you'll just end up with layers and layers of limestone at the bottom of a desolate ocean. Like damn, that would've been pretty nice, wouldn't it?